Custom colors are used in many printing and packaging applications to supplement process colors made by combinations of cyan, magenta, yellow, and black (CMYK). A typical example of a custom color is “Coca-Cola red”.
Customer selectable colors are typically utilized to provide instant identification and authenticity to a document. As such, the customer is usually highly concerned that the color meets particular color specifications. For example, the red color associated with Xerox' digital stylized “X” is a customer selectable color having a particular shade, hue and color value. Likewise, the particular shade of orange associated with Syracuse University is a good example of a customer selectable color. A more specialized example of customer selectable color output can be found in the field of “custom color”, which specifically refers to registered proprietary colors, such as used, for example, in corporate logos, authorized letterhead, and official seals. The yellow associated with Kodak brand products, and the brown associated with Hershey brand products are good examples of custom colors that are required to meet exacting color standards in a highlight color or spot color printing application.
The various colors typically utilized for standard highlighting processes generally do not precisely match customer selectable colors. Moreover, customer selectable colors typically cannot be accurately generated via halftone process color methods because the production of solid image areas of a particular color using halftone image processing techniques typically yields nonuniformity of the color in the image area.
Further, lines and text produced by halftone process color are very sensitive to misregistration of the multiple color images such that blurring, color variances, and other image quality defects may result. As a result of the deficiencies noted above, customer selectable color production in electrostatographic printing systems is typically carried out by providing a singular premixed developing material composition made up of a mixture of multiple color toner particles blended in pre-selected concentrations for producing the desired customer selectable color output. This method of mixing multiple color toners to produce a particular color developing material is analogous to processes used to produce customer selectable color paints and inks. In offset printing, for example, a customer selectable color output image is produced by printing a solid image pattern with a premixed customer selectable color printing ink as opposed to printing a plurality of halftone image patterns with various primary colors or compliments thereof.
The disclosures of custom color for toners in the prior art usually involve mixing toners of different colors together in one developer. This approach has the problem that toners of one color may develop at a greater rate than toners of another color, due to differences in charge, adhesion, or other characteristics, causing a color shift over time. Various means of solving this problem have been disclosed, such as mixing toners directly in the developer to control the final color, or making the toner mixtures compatible by encapsulating the pigments within the toner particle or by applying varying surface treatments to equalize the triboelectrification properties
Several patents describe the apparatus that can be used for mixing differently colored toner particles into a single developer. U.S. Pat. No. 6,751,430 describes a toner purging development apparatus and method for producing custom colors. This patent provides custom colors by removing the first quantity of toner particles having a first color from the sump, and allowing the loading, of a second quantity of toner particles having a second and different color.
U.S. Pat. No. 6,618,654 describes a custom color printing system including an apparatus for developing a latent image with a custom color toner. A replaceable reservoir unit is provided for mixing and supplying the custom color toner to the donor member. An array of toner dispensers is provided for supplying various primary color toners, as required, to achieve the custom color. In such an operational environment, replaceable containers of premixed customer selectable color developing materials corresponding to each customer selectable color are provided for each print job. Replacement of the premixed customer selectable color developer materials or substitution of another premixed color between different print jobs necessitates operator intervention that typically requires manual labor and machine downtime, among other undesirable requirements. In addition, since each customer selectable color is typically manufactured at an off-site location, supplies of each customer selectable color printing ink must be separately stored for each customer selectable color print job.
U.S. Pat. No. 6,292,643 describes a traveling wave transport system that will transport individual toner colors and mixes them before they reach the photoconductor.
U.S. Pat. No. 5,897,239 describes a method to replenish the developer with the correct ratio of the individual color toner components by using calorimetric measurement of the replenished developer.
Chemical means of mitigating the differences in the triboelectric properties of the individual toner components are described in several patents. U.S. Pat. No. 6,413,692 describes preparing toner by preparing encapsulated latexes of individual colors and then carrying out an aggregation step to prepare toner particles. While this method would work, emulsion aggregation is generally restricted to vinyl-based binders and not to the polyester based toners that are preferred for high quality imaging. US Publication 2005/0095521A1 describes the use of surface treatment to equalize the tribocharging properties. While the initial charge of these particles may be the same, aging of the developer usually causes embedment of the surface treatment particles into the toner which will cause their tribocharging properties to be different. U.S. Pat. No. 5,204,208 describes method of applying a polymeric shell to individual colored toners to ‘encapsulate’ the pigment. While this method would succeed, it involves expensive manufacturing processes.
Most color printers have a set of 4 colorants that are used to provide the normal gamut of colors. It is desired that in order to produce a custom color outside this gamut, the toner with the basic color should be utilized and modified to provide the custom color. This invention describes a method of achieving this.
The main object of this invention is to utilize a toner with one of the primary colors and to modify it to produce a custom color.
Another object is to be able to achieve this simply and at a low cost.
Yet another object is that the modified toner of the present invention be durable under aging of the developer and maintain its triboelectric properties.
Yet another object of this invention is to be able to prepare a custom color toner with any suitable binder and with toner made by any conventional or chemical manufacturing method.